This section provides background information related to the present disclosure which is not necessarily prior art.
In both residential and commercial roofing applications, a roofing material is used to provide a weather and water protection barrier. Various roofing materials include composite shingles, metal panels or shingles, concrete or clay tiles, wood shakes, slate, concrete and clay tile, and the like. In certain circumstances, water can penetrate the roofing material due to a primary roofing material design, installation practices, or an accidental breach of the primary roofing material. To protect the building interior in these circumstances, a layer called a roofing underlayment can be provided beneath the layer of roofing material. The roofing underlayment acts as a water and a moisture barrier.
Underlayment can be affixed to a roofing surface, for example, by use of various fasteners such as nails, staples, and the like, or through use of an adhesive. The underlayment can be substantially impermeable to moisture. Additionally, it is desirable for the underlayment to have high tensile and tear strengths to reduce the likelihood of tearing during installation and exposure to high winds. Underlayment can preferably be light in weight to facilitate ease of transport and application, and should be able to withstand prolonged exposure to sunlight, air, and water.
Base sheet underlayment for various roof applications include tar paper felt materials. Although widely used, these felt materials are associated with numerous drawbacks that can diminish the integrity of the roof system. For example, felt absorbs moisture causing physical expansion where the material will buckle and wrinkle. Water can contact felt during installation due to weather exposure and felt can also absorb water after installation, where moisture from inside the structure is generated from various sources, such as cooking, showers, industrial processes, etc. The buckling and wrinkling condition causes felt to load up on any fasteners employed, causing tears or elongation of the felt at the fastener, which can compromise the integrity of the roof system. Felt containing moisture can also support growth of mold and fungus. What is more, felt has no natural protection from UV light and can deteriorate when left exposed to direct solar radiation.
Polymeric roof underlayment materials, such as various polyolefin materials, are available that provide a significant improvement over standard felts. Such synthetic polyolefin materials offer optimum levels of tensile strength, light weight, and improved handling characteristics. Typically a woven or non-woven polyolefin material is coated on either one or both sides with a polymer coating. The polymer composition of the woven material and coating are normally a variation or combination of polyethylene or polypropylene. These polyolefin materials provide several benefits in that they are inert and do not absorb moisture or breakdown when exposed to harsh outdoor elements or chemicals. They can be resistant to rot and can have greatly improved UV resistance in comparison to felt.
A limitation of polyolefin roof underlayments is that these materials can be very slippery in both wet and dry conditions. Installation of the underlayment and the subsequent roofing material can therefore be problematic as workers may need to walk across or work upon the polyolefin material. This decreases the commercial attractiveness of such materials for high pitch roof applications or in climates characterized by wet or humid conditions. Accordingly, it would be desirable to provide a way to form a polymeric roofing underlayment that also provides anti-skid or enhanced friction properties.